With a $200 apiece price tag, I don't think that you'll find much overall experience on them. I persoanlly have only had the opportunity to try the English Muff'n and LOVED IT! I felt that the tubes really helped with the overdrive tone without losing bass response. The pedal could get a mellow overdrive, and all out hell, without losing bass. Keep in mind I had all the EQ set flat for all my tests and soundclips.

cleanpbass.wav is the '78 Precision with Chromes, run clean
cleanmuffn.wav is the P through the Muff'n at a low OD setting
dirtymuffn.wav is the P through the Muff'n at a high OD setting
bigmuff.wav is the P through a stock USA Big Muff Pi for comparison